The present invention relates to ginsenoside Rb1 or its salt useful as cell-protective (cytoprotective) agents. More particularly, the present invention pertains to pharmaceutical compositions comprising ginsenoside Rb1 or its salt for inhibiting apoptosis or apoptosis-like cell death or pharmaceutical compositions comprising ginsenoside Rb1 or its salt for promoting the expression of a cell death-inhibitory or antiapoptotic gene product Bcl-xL. More further particularly, the present invention pertains to pharmaceutical compositions comprising ginsenoside Rb1 or its salt for intravenous administration.
Originally, methods for treatment of cerebral apoplexy (cerebral vascular diseases) are different among cerebral infarction, cerebral embolism, cerebral hemorrhage, transient ischemic attack and subarachnoid hemorrhage, and strictly, no effective countermeasure can be taken unless a cerebral CT inspection is performed. For example, thrombolytic agents can be used only for the treatment of cerebral infarction and cerebral embolism and are regarded as a contraindication for the treatment of cerebral hemorrhage. However, cerebral apoplexy is a serious disease resulting in a permanent disorder of higher functional activities or threatening the survival of patients, if no treatment is performed for protecting nerve cells or neurons at risk in the lesion site as early as possible. Consequently the treatment should be initiated without a moment""s delay. Even the period of time for the CT inspection of brain is, to put it strongly, a factor to make the possibility of recovery smaller for the patients with cerebral apoplexy. Surely, the treatment of acute cerebral apoplexy is a struggle against not only cerebral apoplectic lesion but also a time after its onset. Quite unfortunately, at present, whatever the disease type of cerebral apoplexy (cerebral infarction, cerebral hemorrhage, cerebral embolism, subarachnoidal hemorrhage and transient ischemic attack) is, it is the actual condition that few drugs showing a potent effect, if administered immediately after the onset of cerebral apoplexy, are known.
Ginsenoside Rb1 is a compound having the following chemical structure: 
Ginsenoside Rb1 is a known compound with references, for example, by Shibata et al. (Shibata et al., Economic and medicinal plant research, World Scientific, Philadelphia, pp. 217-284, 1985).
Intraperitoneal administraction of ginsenoside Rb1 has been reported to show a tranquilizing action on the brain (Yoshimura H. et al., Eur. J. Pharmacol., 146, 291-197, 1988), but no mechanism of the action has been elucidated. In the central nervous system, the possibility has been raised that a mixture of ginsenoside Rb1 and ginsenoside Rg1 (or ginsenoside Rb1 or ginsenoside Rg1 at the extracellular concentration from 10xe2x88x926M to 10xe2x88x927M) shows some effect for Alzheimer""s disease as a result of activating acetylcholine-containing nerve cells (U.S. Pat. No. 5,137,878: Composition and method for treatment of senile dementia). However, since it can not be said that the main cause of Alzheimer""s disease is a functional disturbance of acetylcholine-containing nerve cells, this hypothesis has many problems to be solved.
In addition, the nerve cell-protective or neuroprotective action by a single use of ginsenoside Rb1 has scarcely been elucidated until the studies on ginsenoside Rb1 was initiated by us. We have studied until now to show a protective action of ginsenoside Rb1 for the cells other than acetylcholine-containing nerve cells using the transient forebrain ischemia model of gerbils. It has been proved that in this forebrain ischemia model animal, occlusion of the bilateral common carotid arteries for 3 to 5 minutes while maintaining the brain temperature at 37xc2x0 C. results in a neuronal loss of the hippocampal CA1 pyramidal cells (containing no acetylcholine) within one week after ischemia depending on the occlusion time (this event is called delayed neuronal death), and that the learning behavioral function of the ischemic animals is deteriorated (Wen T. -C. et al., Acta Neuropathol., 91, 15-22, 1996). These facts mean that the transient forebrain ischemia model of gerbils reflects the human pathologic condition of transient ischemic attack (TIA).
We have proved that administering ginsenoside Rb1 (10 mg/kg or 20 mg/kg) into the peritoneal cavity of gerbil once a day for one week in advance can significantly prevent delayed neuronal death and learning disability caused by occlusion of the common carotid arteries for 5 minutes (Wen T. -C. et al., Acta Neuropathol., 91, 15-22, 1996). However, intraperitoneal administration of ginsenoside Rb1 immediately after 3- or 5-minute occlusion of the common carotid arteries showed no effect (Wen T. -C. et al., Acta Neuropathol., 91, 15-22, 1996; Lim J. -H. et al., Neurosci. Res., 28, 191-200, 1997). Consequently, since transition rate and transportation rate to -brain of peripherally (intraperitoneally) administered ginsenoside Rb1 are thought to be very low, no clinical application of ginsenoside Rb1 was kept in mind at that stage in view of the protection of hippocampal CA1 pyramidal neurons.
It has been reported that intracerebroventricular infusion of ginsenoside Rb1 starting immediately after occlusion of the common carotid arteries for 3 or 3.5 minutes in place of the above peripheral (intraperitoneal) administration suppresses the delayed neuronal death and learning disability (Lim J. -H. et al., Neurosci. Res., 28, 191-200, 1997). Further, in spontaneous hypertensive stroke-prone (SH-SP) rats with permanent occlusion of the cortical branch of the left middle cerebral artery (MCA) (cerebral infarction model of rats), intracerebroventricular infusion of ginsenoside Rb1 starting immediately after permanent occlusion of the MCA caused a significant reduction of the infarcted area in the cerebral cortex and ameliorated the ischemia-induced place navigation disability of the animals (Zhang B. et al., J. Stroke Cerebrovasc. Dis., 7, 1-9, 1998).
Even though ginsenoside Rb1 is effective in the direct intracerebroventricular infusion, however, it appears impossible to apply ginsenoside Rb1 to human transient cerebral ischemic attack (TIA) and cerebral infarction due to the problems in the route of administration, similarly to other peptide growth factors (Sakanaka M. et al., Proc. Natl. Acad. Sci. USA, 95, 4635-4640, 1998; Wen T. -C. et al., J. Exp. Med., 188, 635-649, 1998).
Concerning the mechanism of neuroprotective action by peripheral (intraperitoneal) administration of ginsenoside Rb1, we have reported that a culture medium previously admixed with a low concentration (1-100 fg/ml) of ginsenoside Rb1 reduces neuronal necrosis caused by a hydroxyl radical inducer (ferrous sulfate) (Lim J. -H. et al., Neurosci. Res., 28, 191-200, 1997; Zhang B. et al., J. Stroke Cerebrovasc. Dis., 7, 1-9, 1998). We have presumed that ginsenoside Rb1 decreases cell membrane lipid peroxides as a result of scavenging hydroxyl radicals to protect cultured nerve cells, but up to now no one proved this hypothesis.
Several reports concerning the neuroprotective effect of ginsenoside Rb1 have been made in culture experiments. For example, high concentrations (0.11-11 xcexcg/ml) of ginsenoside Rb1 reduce glutamate-mediated neurotoxicity to prevent neuronal cell death (Kim Y. -C., et al., J. Neurosci. Res., 53, 426-432, 1998), and a higher concentration, approximately 500 xcexcM (550 xcexcg/ml) of ginsenoside Rb1 has a possibility to prevent apoptosis-like nerve cell death (Tanaka T. et al., The Ginseng Review, 24, 61-65, 1998). However, according to the results of our culture experiments, high concentrations of ginsenoside Rb1 has shown an increased neurotoxicity (Lim J. -H. et al., Neurosci. Res., 28, 191-200, 1997; Zhang B. et al., J. Stroke Cerebrovasc. Dis., 7, 1-9, 1998).
Furthermore, such high concentrations of ginsenoside Rb1 can not be realized in an extracellular fluid in vivo, and we speculate that an administration of a large amount of ginsenoside Rb1 into a human body to maintain the high extracelular concentrations of ginsenoside Rb1 is impossible considering cost and adverse effects. Actually, from our experimental results, it has been proven that a high dose of ginsenoside Rb1 can not always provide preferable efficacy and effectiveness (Zhang B. et al., J. Stroke Cerebrovasc. Dis., 7, 1-9, 1998).
In conclusion, the mechanism of neuroprotection by ginsenoside Rb1 has not been elucidated yet. If the action mechanism of ginsenoside Rb1 can be made clear, it is expected to find out new efficacies and applicabilities of the same agent. Further, it has not been elucidated whether or not ginsenoside Rb1 actually inhibits apoptosis-like cell death at low concentrations.
We have found that ginsenoside Rb1, at such a markedly low concentration range never reported in the world as 1 fg/ml to 100 fg/ml, suppresses apoptosis-like nerve cell death by increasing the expression of a cell death-suppressing gene product Bcl-xL. Namely we have found in the present invention that ginsenoside Rb1 is the only one non-peptidic Bcl-xL expression stimulator in the world. Although ginsenoside Rb1 at the concentration of 100 fg/ml showed a slight suppressive action on the formation of lipid peroxides, no such effect was observed at a lower concentration range. Consequently, the hypothesis heretofore presented in relation to the action mechanism of ginsenoside Rb1 was found inappropriate. We have further found that ginsenoside Rb1 suppresses apoptosis-like nerve cell death in vivo, and completed the present invention.
Namely, we have found that intravenous administration of ginsenoside Rb1 exhibits unexpectedly a superior suppressive action against cerebral infarction and ameliorates infarction-induced place navigation disability.
An object of the present invention is to provide drugs or pharmaceutics which exhibit a superior therapeutic effect on patients with cerebral infarction and a suppressive action for cerebrovascular dementia, and protect cells by facilitating an expression of the cell death-suppressing gene product Bcl-xL.
Another object of the present invention is to provide preparations for efficaciously administering ginsenoside Rb1 or its salt useful as cytoprotective agents.
More particularly, further object of the present invention is to provide pharmaceutical compositions comprising ginsenoside Rb1 or its salt for inhibiting apoptosis or apoptosis-like cell death or pharmaceutical compositions comprising ginsenoside Rb1 or its salt for promoting an expression of the cell death-inhibitory gene product Bcl-xL.
Still further object of the present invention is to provide preparations comprising ginsenoside Rb1 or its salt for intravenous administration useful for the therapy, prevention or treatment of brain and nerve diseases.
The present invention relates to pharmaceutical compositions comprising low concentrations of ginsenoside Rb1 or its salt for inhibiting apoptosis or apoptosis-like cell death.
The present invention further relates to pharmaceutical compositions comprising low concentrations of ginsenoside Rb1 or its salt for promoting expression of the cell death suppressing gene product Bcl-xL.
The pharmaceutical composition of the present invention is preferably preparations for intravenous administration, but other routes of administration can optionally be selected.
The present invention still further relates to pharmaceutical compositions comprising ginsenoside Rb1 or its salt preferably at low extracellular concentrations in lesion for the therapy, prevention or treatment of brain and nervous diseases, and more preferably the present invention relates to preparations comprising ginsenoside Rb1 or its salt for intravenous administration for the therapy, prevention or treatment of the above diseases. Further, the present invention pertains to the hereinbefore described preparations for intravenous administration for the therapy, prevention or treatment of brain and nervous diseases, protective agents or preparations for brain cells or nerve cells, methods for treating or preventing these brain diseases, and to the use of ginsenoside Rb1 or its salt for producing these pharmaceutical compositions.